There are many small historic Slavic nations like Lusatia, Rusin, Kashubia and others. Russia is now the most powerful and populated Slavic country, but in the 10th century Serbs and Czechs were powerful, and in the 16th century Poland was the strongest nation in the area.

The Slavic languages are closely related. The largest similarities can be found within the same group (e.g. Polish and Slovak, both West Slavic languages), but similarities exist even between Slavic languages from other different subgroups (e.g. Bulgarian and Russian). However, the greatest similarities exist between Serbian, Bosnian and Croatian - these South Slavic languages are considered separate by the Bosnian and Croatian governments, but most linguists say they are one language called Serbo-Croatian. Slavic languages are spoken natively by 300 million people, and as second or third languages by many more people in countries as far apart as Germany and China.